Art for providing guidance corresponding to the coordinated lighting of a plurality of traffic signals is currently known. For example, Japanese Patent Application Publication No. JP-A-2001-165684 discloses art in which up to two nodes ahead are used as a reference range. When the traffic signals within the reference range operate in association, such traffic signals are not used to calculate a traffic signal cost, however, when the traffic signals do not operate in association, the traffic signal cost is calculated.    Patent Citation 1: Japanese Patent Application Publication No. JP-A-2001-165684